Project Summary/Abstract: The overall aim of this proposal is to understand the fibrate mechanism of action in diabetes and its complications. Our studies demonstrate that 1) fenofibrate is most potent among all the fibrates tested in inhibiting aldose reductase (AR) activity in vitro; 2) fenofibric acid shows less potency in inhibiting AR catalyzed forward reaction and only in the pH range 5.0- 6.0 unlike fenofibrate; and 3) first structure and binding proof affirms that AR is a drug target for fibrate derivative, WY 14,643. Following oral administration, fenofibrate is rapidly hydrolyzed by esterases to its active metabolite, fenofibric acid. Unchanged fenofibrate (prodrug) has been reported to be undetectable in plasma samples following an oral dose. Fibrates are successful in the treatment of hypertriglyceridaemia or mixed hyperlipidaemia. On the other hand AR is known to play a significant role in diabetes and its complications and numerous attempts to identify inhibitors for the treatment of AR mediated complications have not proven successful. Exposure to high levels of glucose induces the production of reactive oxygen species (ROS) which may modify AR by oxidizing Cys residues to sulfenic acids and the sulfenic acid modified AR shows higher enzyme activity. The objective of this proposal is to evaluate the role of fibrate derivatives in the function of wild-type and C298X mutant AR. The SPECIFIC AIMS are 1) determine the inhibition potency and molecular interactions of fenofibrate derivatives; 2) establish the role of Cys298 in AR enzyme activity in the presence of newly synthesized fenofibrate derivatives, and 3) evaluate the function of the Cys298 modified AR in the presence of fibrate derivatives. The project will combine chemical, biochemical (spectrofluorometric enzymatic assays) and molecular (structural methods) approaches with the use of recombinant and cell culture samples. We expect that the results obtained from these studies will further our understanding of the nature of fibrate mechanism under normal and high glucose conditions.